interesting thread. i don´ t use gps. i have never been interested in it and i don´ t understand why people track every single run.
for me: important workouts, specific interval stuff is on the track or in the forrest (minute runs or 200m - 400m paths measured with a measuring tape), all the other runs just by duration, feel and effort. sometimes i look up in a hiking map the length of a run out of curiosity, a few years ago i have started to use an internet tool here and then to measure my routes where i do my time trials.
i am pretty sure that even without any measurement my estimated mileage is about quite right. i am not interested in getting in a specific mileage, i just want to look back at the end of the week and check if i have completed my schedule and my workouts.